This invention generally relates to the treatment of arrhythmia and particularly an intravascular method and system for treating arrhythmia.
Prior methods for treating a patient's arrhythmia include the use of antiarrhythmic drugs such as sodium and calcium channel blockers or drugs which reduce the Beta-adrenergic activity. Other methods include the surgically sectioning the origin of the signals causing the arrhythmia or the conducting pathway for such signals. More frequently, however, in order to terminate an arrhythmia the arrhythmogenic site which causes the arrhythmia or conductive pathways which propagate aberrant signals are destroyed by heat, e.g. applying a laser beam or radio frequency (RF) energy to a desired location on the patient's endocardium. A major problem of ablating the origin of the signals or a conductive pathway is to accurately determine the location of the site so that an excessive amount of good tissue is not destroyed adjacent the site.
For example, the average arrhythmogenic site consists of about 1.4 cm.sup.2 of endocardial tissue, whereas a re-entrant site might be much larger. RF ablation techniques produce lesions about 0.5 cm.sup.2 in diameter, so a number of lesions might be generated in order to completely ablate the area of interest. If the site is not accurately mapped, much of the good tissue surrounding the site will be unnecessarily destroyed.
Other methods to terminate arrhythmia have been tried but they have not been used clinically to any great extent for a variety of reasons. For example, ethanol may be injected into a branch of a coronary artery which feeds an arrhythmogenic region of the patient's heart or a conductive pathway therein to occlude the arterial passage and create a controlled infarct at the arrhythmogenic site or the conductive pathway to terminate the arrhythmia. However, due to reflux of the ethanol, it is not always possible to control the region of cytotoxic activity within the heart. Additionally, over time, it has been found that the occluded arterial passageway frequently is subject to recanalization which can allow the arrhythmia to return.
What has been needed is an effective method and system for permanently occluding a portion of a patient's coronary artery which feeds the tissue of a patient's heart causing the arrhythmia, such as an arrhythmogenic or re-entrant site or a conductive pathway, in order to the terminate an arrhythmia.